1884.] 
upon Vegetation. 
587 
their seed-leaf at 35^° F. (2 0 C.) though the root showed at 
32° F. Maize, as might be expected, required the highest 
temperature among the cereals ; it only began to germinate, 
and that slowly, at 47^-° F. (87° C.). 
Rape germinated at 32° F. ; flax at 35^° F. ; tares sprouted 
well at 32 0 F. ; peas and clover at 35^-° F. ; beans and carrots 
at 37F F. ; whilst cucumber seeds showed no signs of 
germination even at 47^° F. 
It must not be supposed that these results throw any 
light upon the temperatures required for the further deve- 
lopment of the different species of plants. Further experi- 
ments were made in this direction with barley-seedlings. 
A series of flower-pots was taken, of which a was kept con- 
stantly in a water-bath at 50° F. (io° C.), b in one at 68° F. 
(20° C.), c in a similar bath at 86° F. (30° C.), d in one at 
104° F. (40° C.), and e stood in a water-bath exposed to the 
fluctuating temperature of the atmosphere. In each pot 
were set two barley-seedlings, the soil and the water-supply 
being of course identical in every case. The experiment 
was continued from August 9th to November 9th, when the 
plants were pulled and analysed. 
The plants in e showed a healthy, equable growth, and a 
good colour, and were evidently quite normal. Very similar 
were the plants in b (at 68° F.). Those in a grew unusually 
slowly, whilst the plants in c grew very rapidly. The former 
of these two lots, however, were of a deep luxuriant green, 
whilst the latter were duller and paler in colour. The plants 
in d, exposed to a constant bottom-heat of 104° F., were 
pale and sickly, and lagged behind in their growth. This 
temperature had evidently an injurious effect. For barley, 
therefore, a temperature of 68° F. seemed the optimum 
point, whilst 50° and 86° F. could not be pronounced hurtful. 
Similar experiments were made with the seedlings of 
other cereals. It was found that wheat, in its first period 
of growth, requires a considerably higher bottom-heat than 
rye, — a result which agrees substantially with observation 
made in the fields in ordinary agricultural practice. 
For rye in the first period of growth assimilation was 
found to be most active at 68° F., for barley 77 0 F., and for 
wheat at 86° F. 
The question was next raised whether, and if so to what 
extent, transitory higher temperatures affeCt the growth of 
plants injuriously. 
The various physiological functions of vegetable life are 
not all best effected under the same conditions of heat and 
light, but require unequal quantities of both. Thus the 
2 y 2 
